1. Field of the Invention
The present invention relates to a transporter having track-axles in order to carry very heavy loads. More particularly, the present invention relates to a transporter having multiple track-axles that have independent suspension, self-loading, and on-center axle rotation capability in order to carry very heavy loads without damaging the transport surface.
2. Description of the Related Art
Industrial facilities, including factories, power plants and shipyards, often require that very large, heavy and often delicate objects be moved both within buildings of the industrial facility and between buildings.
One method in which very heavy objects can be moved within an industrial facility is through the use of cranes. One example of a crane used in an industrial facility is a gantry crane which includes a hoist in a trolley running horizontally along gantry rails. The gantry crane has the disadvantages of a large size, especially height, and a lack of maneuverability. Another example of a crane used in an industrial facility is an overhead crane system including beams mounted on the side walls of a building. In the overhead crane system, the hoist is on a trolley which moves along the beams. A disadvantage of the overhead crane is that objects cannot be transported from one bay to another or outside of the building beyond which the overhead crane's track system extends.
Another method of moving objects within an industrial facility is through the use very heavy capacity fork lifts and heavy capacity trailers, both of which require extended operating space and place heavy point-loading on the operating surfaces.
Heavy capacity fork lifts typically have solid tires, or limited mechanically equalizing suspension relying on compression of the tires for compliance to uneven operating surfaces. Very heavy capacity solid tire trailers are limited to mechanical equalizing suspension, therefore providing limited compliance and maneuverability on irregular floors and congested spaces. The latter have sharply diminishing capabilities for loads rise above 40 tons.
For the transport of very heavy loads within an industrial facility, where loads are generally in excess of 80 tons, In Plant-Self-Propelled Modular Transporters (IP-SPMT) may be utilized. An IP-SPMT refers to a low-profile deck, multi-axle, self-propelled transporter, with independent suspension axle assemblies that are typically used to carry loads heavier than 80 tons and ranging into hundreds of tons. An IP-SPMT is typically internal combustion engine-electric powered and has six to twelve or more on-center rotation axle assemblies. The axles can be independently steered by varying each wheel motor speed and direction.
However, in certain applications, existing movers and IP-SPMT devices are not sufficient because their wheels can overload the operating surfaces. One proposed solution is to use air bearings or the like which require special surface preparations. Another proposed solution is to use tracked type vehicles which lack the maneuverability and have much larger space requirements.
The inventor of the present invention has previously proposed an IP-SPMT in U.S. Pat. No. 5,379,842 capable of carrying very heavy loads of over 80 tons to address some of the shortcomings of the prior art. In the material-handling equipment of U.S. Pat. No. 5,379,842, a multi-wheeled transport vehicle capable of carrying very heavy loads while crossing uneven terrain without torquing the load was disclosed. The material handling equipment included a modular wheel unit 5 shown in FIG. 1. The modular wheel unit 5 permitted a low profile and included means 7 to equalize the load between the individual wheel units.
However, the material-handling equipment of U.S. Pat. No. 5,379,842 utilized solid urethane tires 9 with tire surface contact pressures ranging typically from 600 to 900 psi. The use of those existing design axle assemblies result in contact pressures that can create rutting in asphalt road surfaces, possibly requiring the users to resurface the roadway after use or to replace their roadbed with concrete surfaces designed to take the specific wheel loading. For example, when a spent nuclear fuel container weighing over 80 tons is required to be moved from a fuel building of a power plant to an Independent Spent Fuel Storage Installation (ISFSI), the heavily shielded nuclear fuel container must typically be moved 1,000 to 5,000 feet or more from the fuel building. Roadbeds leading to the ISFSI spent fuel storage locations are typically asphalt and often require the roads to cross buried utility trenches, which are both situations raising concern for tire contact pressure.
Accordingly, it is desired to have a transporter which can carry very heavy loads while reducing the contact pressure on the roadway, while at the same time providing a high degree of maneuverability.